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Geothermal Resources Council
TRANSACTIONS,VOl. 9 - PART II, August 1985
PROJECT DEVELOPMENT DESERT PEAK
C. P. D i d d l e and W.
C. Gonser
P h i l l i p s Petroleum
ABSTRACT
D e s e r t Peak and an o b j e c t i v e t o g e n e r a t e
most power a t t h e l o w e s t c a p i t a l c o s t .
I n l a t e 1982 P h i l l i p s P e t r o l e u m Company
began p r e l i m i n a r y d e s i g n o f a power p l a n t f o r
Desert
Peak
in
Churchill
County,
Nevada.
Because each g e o t h e r m a l r e s o u r c e i s unique,
careful
consideration
of
existing
process
schemes and- d e s i g n t e c h n o l o g i e s was r e q u i r e d .
T h i s p a p e r w i l l r e v i e w p r o c e s s s t u d i e s , examine
some o f t h e d e t a i l d e s i g n and d i s c u s s t h e cons t r u c t i o n program.
No a t t e m p t w i l l be made t o
d i s c u s s g e o l o g i c a l a s p e c t s of t h e r e s o u r c e .
C o o l i n g Towers v s A i r F i n Exchangers
T a b l e 2 summarizes e l e c t r i c a l power p r o duced by a s y s t e m c o o l e d by e i t h e r a i r f i n
e x c h a n g e r s o r c o o l i n g tower.
Table 2
A i r F i n / C o o l i n g Tower E l e c t r i c a l Power
P r o d u c t i o n Comparison
E l e c t r i c a l Power
G r o s s Power Output KWH
P a r a s i t i c KWH
Net Power f o r S a l e KWH
D i f €e r e n c e
Effectiveness
INTRODUCTION
P h i l l i p s P e t r o l e u m Company h a s o b t a i n e d
Federal
and
a p p r o x i m a t e l y 24,000
a c r e s of
S o u t h e r n P a c i f i c R a i l r o a d l e a s e s i n t h e BradyHazen Known Geothermal Resource Area (KGRA), a n
a r e a commonly r e f e r r e d t o a s D e s e r t Peak.
This
medium t e m p e r a t u r e h o t w a t e r dominated r e s o u r c e
i s l o c a t e d i n a r i d r o l l i n g d e s e r t o f t h e Hot
S p r i n g s Mountains, 65 m i l e s n o r t h e a s t o f Reno,
Nevada.
A f t e r preliminary e v a l u a t i o n s of t h e
r e s o u r c e , P h i l l i p s began i n l a t e 1982 a compreh e n s i v e s t u d y o f a l t e r n a t i v e s which u l t i m a t e l y
r e s u l t e d i n t h e c u r r e n t 9 Mw f a c i l i t y d e s i g n .
A i r Fin
7279
1509
5770
(3496)
62%
Coo 1i n g
Tower
10022
756
9266
A l s o , t h e c a p i t a l c o s t o f t h e c o o l i n g tower
was one t h i r d o f t h e c o s t o f t h e a i r f i n exchangers.
Two Phase Flow v s Wellhead S e p a r a t i o n
Wellhead s e p a r a t o r s y s t e m s and two p h a s e
flow s y s t e m s were s t u d i e d t o d e t e r m i n e which
could provide t h e lowest p r e s s u r e drop a t t h e
l o w e s t i n v e s t m e n t and o p e r a t i n g c o s t s .
Two
phase flow was s e l e c t e d b e c a u s e o p e r a t i n g and
i n v e s t m e n t c o s t s were r e d u c e d by e l i m i n a t i n g
wellhead s e p a r a t o r s .
By l o c a t i n g t h e p l a n t
d o w n h i l l o f t h e p r o d u c t i o n w e l l s and i n s u r i n g
t h e r e were no p o c k e t s i n t h e l i n e ; damage due t o
s l u g f l o w was e l i m i n a t e d .
Large d i a m e t e r p i p e s
also assisted i n separating fluids.
Process Parameters
T a b l e 1 shows p r o c e s s p a r a m e t e r s u t i l i z e d
f o r D e s e r t Peak.
Table 1
P r o d u c t i o n Well C h a r a c t e r i s t i c s
Average f l o w r a t e p e r w e l l
Average w e l l h e a d temp
Average w e l l h e a d p r e s s u r e
Average r e s o u r c e temp
Average r e s o u r c e e n t h a l p y
Steam f l a s h by mass
the
500,000 lbm/hr.
3 2 60F
97 PSIA
400°F
384 BTU/lb
9.9%
F l o a t i n g Power
is
F l o a t i n g power means
t h a t equipment
s i z e d t o t a k e advantage of temperature ranges.
As t h e c o o l i n g s y s t e m r e s p o n d s t o lower temperat u r e s more horsepower c a n be developed by t h e
t u r b i n e and more power c a n b e g e n e r a t e d .
When
f l o a t i n g power i s c o n s i d e r e d , t h e p r o d u c t i o n
rate
remains
constant;
however,
temperature
f l u c t u a t i o n s a r e r e f l e c t e d by a n n u a l i z e d mean
termperatures.
T a b l e 3 summarizes d e s i g n c o n d i t i o n s and power o u t p u t .
Studies
The p r o c e s s s p e c i f i c a t i o n f o r D e s e r t Peak
e v o l v e d from c r i t e r i a e s t a b l i s h e d by P h i l l i p s
Geothermal Branch and p r o c e s s s t u d i e s .
Each
s t u d y was based upon e x i s t i n g c o n d i t i o n s a t
127
D i d d l e et a l .
Table 3
C o n s t a n t P o w e r / F l o a t i n g Power Comparison
Conditions
P r o d u c t i o n r a t e lbm/hr
C o o l i n g Water t o
Process
Coo 1i n g Wa t e r
from P r o c e s s
E l e c t r i c a l Power
Net Power KWH
Percent increase
Constant
Power
Floating
Power
1,086,000
1,086,000
670F( 1 )
1070F( 1
10,000
53OF( 2 )
930F( 2,
11,050
10.5%
( 1 ) Summer c o n d i t i o n s
( 2 ) Mean a n n u a l
high pressure separator.
Excess b r i n e i s f l a s h e d i n t h e low p r e s s u r e s e p a r a t o r .
Low p r e s s u r e
s t e a m from t h e RST and low p r e s s u r e s e p a r a t o r
enters
the
s t e a m t u r b i n e a f t e r any e x c e s s
m o i s t u r e is removed by a knock o u t v e s s e l .
Steam a t less t h a n a t m o s p h e r i c p r e s s u r e i s d i s c h a r g e d from t h e s t e a m t u r b i n e i n t o a d i r e c t
c o n t a c t s p r a y c o n d e n s e r where vacuum i s p r o v i d e d
Heat i s r e j e c t e d t h r o u g h a
by s t e a m e j e c t o r s .
c o o l i n g tower and make up f o r t h e s y s t e m i s condensate.
B r i n e from t h e RST flows t o t h e low
pressure
separator.
The
injection
system
i n c l u d e s t h e d i s c h a r g e from t h e second s t a g e
s e p a r a t o r , c o o l i n g t o w e r blow down, i n j e c t i o n
F i g u r e 3 shows t h e
pumps and a n i n j e c t i o n w e l l .
plant layout.
B i n a r y v s F u l l Flow U n i t
P h i l l i p s compared a n i n t e r n a l l y d e s i g n e d
b i n a r y system w i t h a r o t a r y s e p a r a t o r t u r b i n e
(RST) s y s t e m .
RST power s k i d o p e r a t i n g parame t e r s were p r o v i d e d by T r a n s a m e r i c a D e l a v a l
B i p h a s e Energy Systems and P h i l l i p s d e v e l o p e d
t h e p r o c e s s f l o w s h e e t f o r t h e system.
The RST
p r o c e s s was s e l e c t e d p r i m a r i l y b e c a u s e i t produced more n e t power a t a lower c a p i t a l c o s t .
T a b l e 4 summarizes b o t h p r o c e s s e s .
Table 4
Binary/RST Comparison
Binary
RST
System C h a r a c t e r i s t i c s
W e l l f l o w lbm/hr
1,500,000 1,500,000
I s o b u t a n e f l o w lbm/hr
2,026,000
Cooling water c i r c u l a t i o n
r a t e lbm/hr
12,865,000
6,488,620
E l e c t r i c a l Power
15.08
13.46
G r o s s MW
P a r a s t i c MW
4.10
1.40
N e t f o r s a l e MW
10.98
12.06
Conversion E f f i c i e n c y
Net
7.09%
7.32%
E s t i m a t e Cost D i f f e r e n t i a l
(1982 c o s t s )
$7,200,000
Base
NOTE: Geothermal f l u i d was c o o l e d t o a p p r o x i m a t e l y 1670F i n t h e b i n a r y s y s t e m t o accomodate
minimum i n j e c t i o n t e m p e r a t u r e .
C u r r e n t Design
The c u r r e n t d e s i g n i s t h e r e s u l t o f implementing t h e co n cl u s i o n s of p r e v i o u s l y d i s c u s s e d
studies.
F i g u r e 1 shows t h e 24 i n . and 30 i n .
two p h a s e g a t h e r i n g s y s t e m w i t h the p i a n t
As shown by
located a t the lowest elevation.
Figure 2 geothermal f l u i d s a r e separated i n t o
h i g h p r e s s u r e s t e a m and b r i n e i n t h e h i g h pressure separator.
High p r e s s u r e s t e a m f l o w s
t h r o u g h a knock o u t v e s s e l t o t h e s t e a m t u r b i n e
inlet.
B r i n e from t h e h i g h p r e s s u r e s e p a r a t o r
i s d i v i d e d between t h e RST and t h e low p r e s s u r e
separator.
Because o f low s y s t e m p r e s s u r e , t h e
RST c a n n o t p r o c e s s a l l b r i n e produced i n t h e
FIGURE 1
DESERT PEAK
PLOT PLAN
Diddle e t a l .
I
I
l
-
l
-
9 MW
FIGURE 2
PROCESS FLOW AND MATERIAL BALANCE
De se r t Peak S i m u l a t o r
P r o c e s s s t u d i e s , p r o c e s s d e s i g n and d e t a i l
d e s i g n c o u l d n o t h a v e b e e n accomplished i n t h e
s h o r t t i m e a l l o c a t e d i n t h e p r o j e c t schedule i f
t h e Desert Peak S i m u l a t o r (DPSIMF) had n o t b e e n
developed.
The s i m u l a t o r d e v e l o p e d by C. P.
D i d d l e , P h i l l i p s P e t r o l e u m Company models s i n g l e
f l a s h , d u a l f l a s h and RST s y s t e m s from product i o n wellliead(s)
to
the
i n j e c t i o n wellhead
i n c l u d i n g a l l a u x i l i a r y systems.
I t s program i s
w r i t t e n i n BASICA f o r u s e on t h e IBM PC.
Table
5 shows t h e v a r i a b l e s which c a n b e changed by
t h e e n g i n e e r w i t h i n p u t from t h e keyboard.
The
t e m p e r a t u r e , p r e s s u r e , flow, and p e r c e n t v a p o r
a t t h e top of t h e wellhead a r e given conditions
which c a n b e changed f o r d i f f e r e n t r e s e r v o i r s .
The r e m a i n d e r o f t h e v a r i a b l e s a r e s e l e c t e d by
t h e process engineer.
-
HIOH PRESSURE SEPARATOR
ROTARY SEPARATOR TURBINE
DUAL STAOE STEAM TURBINE
ELECTRICAL OENERATOR
DIRECT CONTACT SPRAY COND.
CONDENSATE C .M .PUMPS
TURBINE ORAIN TANK
1
The program p r o v i d e s f o r change of v a r i a b l e s which a r e l i s t e d by l e t t e r c o d e s .
An
i n p u t w i l l r e s u l t i n a q u e s t i o n t o b e answered
f o r a l l c o d e s e x c e p t : ( 1 ) XT = GET OUT OF THE
SIMULATOR, ( 2 ) RUNS = Causes t h e program t o r u n
a f t e r c h a n g e s o f v a r i a b l e s a r e c o m p l e t e and a
FIGURE 3
DESERT PEAK-EQUIPMENT LAYOUT
ORAIN TANK PUMPS
COOLINO TOMER
COOLINO TOWER WATER PUMPS
NEUTRAL OROUNOINO RESISTORS
RATOR OR
PACKAQEO INST. L TOOL AIR SKID
f
129
TURBINE EXHAUST DUCT
DIK:::
18
POWER HOUSE
SWITCHOEAR BLOO.
8
CONTROL ROOM b OFFICE
RST DRAIN POND
PACKAOE POWER OENERATION SKID
Diddle k t a l .
Table 5
Engineers Input Screen
ENTER VARIABLE CODE LETTERS?
THIS PROGRAM I S A RST/STEAM TURBINE POWER PLANT SfMULAToR + DPSIMFD
******
............................................................................
*
D e s i g n e r o f S i m u l a t o r : Courtney D i d d l e ; P h i l l i p s P e t r o l e u m Co.
SIMULATOR INPUT VARIABLES -- SYMBOLS ( u s e CAPITAL LETTERS)
*
TO INITIALIZE = INT t h e n ENTER = Base Case VALUES
*
We 1l h e a d Temperature
= WT
H I . P r e s s . Sep. Temp.
= FA1
*
We 1l h e a d F l a s h
= vo
Low P r e s s . Sep. Temp.
= F1
*
= FW
W e 1l h e a d Flow
RST INLET Temperature
RST Enhance Stm, LBS.
RST E f f i c i e n c y F a c t o r
H.P. Steam Vent LBS/HR
Stm Turb. O u l e t Temp.
C o o l i n g Two. H20 Temp.
Spray Cond Pump d e l P
Blowdown Pump d e l t a P
RETURN TO STARTING MENU
RUN NUMBER
ENTER - Your NAME
= FA
= VST6
= N1
RST Feed Rate, LBS/HR
RST Feed L i q u i d F a c t o r
Steam E j e c t o r , LBS/HR
L.P. Steam Vent LBS/HR
Steam Turb. E f f i c i e n t y
Pump E f f i c i e n c y
C o o l i n g Twr Pump d e l t a P
R e - I n j e c t i o n Pump d e l t a P
GET OUT OF THE PROGRAM
RUN SIMULATOR
ENTER - P l a n t S i t e NAME
=
=
=
=
=
RSTF
FS
SJ
VL
N2bN3
PEFF
DP2
DP4
XT
RUNS
*
*
*
= VH
*
= F6
*
= F7
=
*
= DP1
=
*
= DP3
=
*
= MU
=
*
= RUNA
=
*
= N$
= S$
*
............................................................................
ENTER VARIABLE CODE LETTERS?
run is desired.
( 3 ) RUNA = Allows f o r a n o v e r r i d e o f t h e Run Number, s i n c e t h e program w i l l
a u t o m a t i c a l l y i n c r e m e n t t h e r u n number by one
( 1 ) e a c h RUNS.
The s i m u l a t o r c o n t a i n s a s t e a m t a b l e w i t h
s a t u r a t e d d a t a between 32-705 d e g r e e s F.
The
program w i l l i n t e r p o l a t e a s a f u n c t i o n o f t e m perature.
Output i s i n t h e form o f a s i n g l e
page summary ( T a b l e 6 ) which i n c l u d e s g r o s s ,
n e t and p a r a s i t i c power o r a s i x page d e t a i l e d
printout.
D e t a i l s include process parameters
o f a l l m a j o r components, pump horsepower, and
power d e v e l o p e d by RST and steam t u r b i n e .
Table 6
S i n g l e Page Power Summary Sequence
*****************~*******************************
ENTER VARIABLE CODE LETTERS ? RUNS
The DPSIMF SIMULATOR i s now c a l c u l a t i n g t h e
problem.
Deserk Peak G r a p h i c S i m u l a t o r
P h i l l i p s i s c u r r e n t l y developing an i n t e r a c t i v e g r a p h i c s i m u l a t o r o f t h e Desert Peak
It w i l l a l s o be a b l e t o s i m u l a t e
process.
s i n g l e f l a s h and d u a l f l a s h s y s t e m s .
The advantage of the graphic simulator is t h a t v a r i a b l e s
c a n b e i n c r e a s e d or d e c r e a s e d by h o l d i n g o n e ' s
f i n g e r on t h e a p p r o p r i a t e key.
As the v a r i a b l e
changes t h e e n g i n e e r c a n o b s e r v e c o r r e s p o n d i n g
changes i n power p r o d u c t i o n and o t h e r s y s t e m
parameters.
Detail Design
S e v e r a l c h a n g e s t o p r o j e c t p r e m i s e s were
made t o accomodate s o l u t i o n s t o problems which
were s o l v e d d u r i n g d e t a i l d e s i g n .
The i m p a c t o n
o t h e r equipment s p e c i f i c a t i o n s were d e t e r m i n e d
by DPSIMF which p r o v i d e d f o r maximizing n e t
power a t a l l times.
*************************************************
THIS PROGRAM I S A RST-STEAM TURB POWER PLANT
SIMULATOR = DPSIMFD
Designer of Simulator: Courtney Diddle
P h i l l i p s Petroleum Co.
DATE OF RUN = 02-22-1985
TIME OF RUN = 08:28:00
RUN NO. = 1
ENG'R:
J. Q. ENGINEER
SUMMARY OF POWER OUTPUT I N KILOWATT HOURS
SITE = ANYWHERE, WORLD
=
657.7
RST POWER AT N1 EFF.
=
5457.0
HI.PR. TURB AT N2 EFF.
L.P. TURN AT N 3 EFF.
=
4046.4
= 10161.2
GROSS POWER-TOTAL POWER
TOTAL PARASITIC POWER
NET POWER FOR SALE
Number o f V a r i a b l e CHANGES
(Maximum = 5 d i f f e r e n t )
=
-
714.8
9446.3
0.0
.................................................
L i q u i d a t s a t u r a t i o n t e m p e r a t u r e and p r e s sure leaving the f i r s t stage separator is flashed due t o n o r m a l p r e s s u r e d r o p i n p i p i n g e n r o u t e
t o t h e RST.
This could cause unequal d i s t r i b u t i o n o f l i q u i d t o RST n o z z l e s .
After study, a
c o o l e r c o n d e n s a t e i n j e c t i o n s y s t e m was d e s i g n e d
t o b e used i f r e q u i r e d .
The DPSIMF c a l c u l a t e d
q u a n t i t i e s of l i q u i d f l a s h e d and q u a n t i t i e s o f
c o n d e n s a t e r e q u i r e d t o lower t h e t e m p e r a t u r e t o
match t h e e x p e c t e d p r e s s u r e a t t h e RST i n l e t .
7hp vent-relief s y s t e m is e s s e n t i a l for the
management o f steam d u r i n g t h e s t a r t - u p o f t h e
Low p r e s s u r e
RST and d u a l s t a g e steam t u r b i n e .
steam w i l l be vented while t h e t u r b i n e i s
s t a r t e d u t i l i z i n g h i g h p r e s s u r e steam.
Optimiz a t i o n of t h e s i z e o f t h e vent c o n t r o l v a l v e s
was a c c o m p l i s h e d by c a l c u l a t i n g t h e e x p e c t e d
flow r a t e s a s a function o f changing back pressure.
The c a l c u l a t i o n was made by t h e DPSIMF
simulator.
I S A HARDCOPY REQUIRED? Y OR N?
130
Diddle et al.
In order to meet excepted operating conditions the brine disposal ponds which were
premised to be installed if required have been
constructed. Diverting production to the ponds
will assist in limiting the rate of the
increase in the systems temperature during
start-up. Also solids loosenedby well cleaning
can be prevented from entering production
pipelines and equipment.
As the operating and startup procedures
developed, it was determined that a distributed
control and permissive interlock systems would
be required. A programable controller with 8K
memory and 128 1/0 points was selected to
implement shut-down logic and permissive start
sequencing. The process will be controlled by
4 eight loop programable controllers.
A CRT
station will be used to monitor and make
process adjustment. Because the system floats
on the wet bulb temperature and production
characteristics change as the result of well
scaling all systems must be kept in balance and
have a reasonable operation range. It would be
impossible to manually control this dynamic
system.
Construct ion
The overall project schedule was developed
to take advantage of all tax incentives and be
operational by December 31, 1985. In order to
meet this objective the construction philosophy
provide for separate site preparation, plant
erection, insulation and painting contracts.
Site preparation was completed in mid March
1985 and the main contract was awarded in early
April.
The RST power skid is scheduled to be
shipped by mid-July and plant start-up is
scheduled for December.
Re ference s
Phillips Petroleum Company Computer Programs
a) DPSIMF RST-Steam Turbine Power Plant
Simulator
b) DPGSIM RST-Steam Turbine Power Plant
Graphic Simulator
Cerini, D. J., Diddle, C. P. and Gonser, W. C.
Project Development Desert Peak 9MW Power
Plant Proceedings Eight Annual Geothermal
Resources Council pgs. 33-39, 1984.
131